There appears to be a routing problem between UCSD and some commercial ISPs. UCSD’s upstream provider, CENIC, has received similar reports from other southern California schools and is investigating. They believe a problem exists with ther peering connections to some ISPs and are actively working on the problem
UCSD is working on this problem. for up to date information please visit the UCSD status page: http://status.ucsd.edu.
we will update this post when more information is available.
UPDATE: 2011-11-20 13:51:11
CENIC believes they have mitigated the problem, restoring proper access to/from campus and the ISPs.
They isolated the issue to a problem with the routing peering at their Los Angeles location. To mitigate, they shifted the paths for this traffic to flow over their Sunnyvale peering.
Once they identify the root cause in LA and fix that, they’ll need to shift traffic back to the original paths through LA. It is unknown yet whether it is a hardware, software, or configuration issue in LA.